horizon replaced nodejs by a python alternative

since commit a0739c9423a4c559b45af96fa4cdb30539dcdbd7 and the Havana
release, horizon uses a pure Python alternative to nodejs.

Horizon changed the way to use the compress utility, the option
offline_compress is no longer available.
Thanks to Maxime Vidori for the information.

Change-Id: Ie290701b00c97352838e13182b940a6de46a591f